Github user spmallette commented on the issue:
https://github.com/apache/tinkerpop/pull/883
That's fair - changed now so that you get this if "graphson" isn't set:
```text
[exec] Error: Hook 'prepare_traversal_source' from
/home/smallette/git/apache/incubator-tinkerpop/gremlin-python/target/python2/radish/terrain.py:66
raised: 'ValueError: test configuration requires setting of
--user-data="graphson=*" to one of [v2,v3]'
[exec]
[exec] Traceback (most recent call last):
[exec] File
"/home/smallette/git/apache/incubator-tinkerpop/gremlin-python/target/python2/env/local/lib/python2.7/site-packages/radish/hookregistry.py",
line 121, in call
[exec] func(model, *args, **kwargs)
[exec] File
"/home/smallette/git/apache/incubator-tinkerpop/gremlin-python/target/python2/radish/terrain.py",
line 70, in prepare_traversal_source
[exec] raise ValueError('test configuration requires setting of
--user-data="graphson=*" to one of [v2,v3]')
[exec] ValueError: test configuration requires setting of
--user-data="graphson=*" to one of [v2,v3]
```
also, if you don't have a good value for "graphson" then you get:
```text
[exec] Error: Hook 'prepare_traversal_source' from
/home/smallette/git/apache/incubator-tinkerpop/gremlin-python/target/python2/radish/terrain.py:66
raised: 'ValueError: serializer set with --user-data="graphson=v2" must be one
of [v2,v3]'
[exec]
[exec] Traceback (most recent call last):
[exec] File
"/home/smallette/git/apache/incubator-tinkerpop/gremlin-python/target/python2/env/local/lib/python2.7/site-packages/radish/hookregistry.py",
line 121, in call
[exec] func(model, *args, **kwargs)
[exec] File
"/home/smallette/git/apache/incubator-tinkerpop/gremlin-python/target/python2/radish/terrain.py",
line 77, in prepare_traversal_source
[exec] raise ValueError('serializer set with
--user-data="graphson=v2" must be one of [v2,v3]')
[exec] ValueError: serializer set with --user-data="graphson=v2" must
be one of [v2,v3]
```
---
